Fix 4 classes of issues that prevented JobEngine from auto-migrating:
1. Non-idempotent DDL: add IF NOT EXISTS to CREATE TABLE, wrap CREATE
TYPE in DO blocks with EXCEPTION WHEN duplicate_object, wrap partition
creation with EXCEPTION WHEN duplicate_object OR SQLSTATE '42P17'
2. Reserved keyword: quote `window` column name in 004_slo_quotas.sql
3. Invalid syntax: replace DELETE...LIMIT with ctid subquery pattern
in 004_slo_quotas.sql and 005_audit_ledger.sql
4. Partition constraint: add tenant_id to UNIQUE(log_id) constraint
on pack_run_logs in 006_pack_runs.sql (partitioned tables require
partition key in all unique constraints)
5. Non-immutable index predicate: remove NOW() from partial index
predicate in 002_backfill.sql
6. Remove BEGIN/COMMIT wrappers from all migration files (the
StartupMigrationHost already wraps each migration in a transaction)
All 8 orchestrator migrations (001-008) now apply cleanly on fresh DB.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
